Magnetic compass



G. R. C. CAMPBELL AND G. T. BENNETT.

g. r. CAMPBELL. ADMINISTRATOR or e. n. c. CAMPBELL, own.

MAGNETIC COMPASS.

APPLICATION FILED IULYI 1919. 1,341,296 I Patented May 25,

GEORGE RICHARD COLIN CAMPBELL, DE

EDWARD FITZHARDINGE CAMPBELL,

CEASED, LATE OF SLOUGH, ENGLAND, BY ADMINISTRATOR, OF MOY,

1311mm), AND

GEOFFREY THOMAS BENNETT, OF SLOUGH, ENGLAND.

MAGNETIC COMPASS.

Application filed m 1,

T0 all/whom it may concern:

Be it known that GEORGE RICHARD COLIN CAMPBELL, late of Slough, in the county of Bucks, England, a subject of the King of Great Britain, jointly with GEOFFREY THOMAS BENNETT, a subject of the King of Great Britain, residing at The Admiralty Compass Observatory, Slough, in the county of Bucks, England, have invented a new and useful Improved Magnetic Compass, of which the following is a specification.

In all liquid ma netic compasses so far constructed the nee le or needle system will, on being deflected from its position of rest, execute a series of diminishing oscillations about that position before settling. The oscillatory motion of all such compasses is, for small amplitudes, of the type known as damped harmonic. In this type of motion the magnetic restoring couple is proportioned to the angular displacement from the equilibrium position, and the resistance due to the damping of the liquid is, for slow movements, proportional tothe angular velocity. According as this damping resistance is below or above a certain amount, for any given angular velocity, the resulting motion is one of two distinct types. If the damping is below the critical value the needles will oscillate isochronously on each side of the equilibrium position with continually diminishing amplitude. But if the damping is .above the critical value the needles will return direct to the equilibrium position witho ut oscillation. Such a motion is said to be aperiodic; and conditions adequate to secure this type of motion are produced in the compass forming the subject of this invention.

It is to be understood that if the liquid itself be in circulation, as from previous rotation of the bowl, or from the stirring action of the filaments during a wide swing, the needles may move past the meridian and return thereto; but that this motion, though temporarily oscillatory, is definitely aperiodic.

The amount of damping requisite to produce aperiodic motion in stationary liquid is obtained according to the invention by attaching to the needles a radial filament or filaments made of glass, wire, or other suitable material, in contradistinction from ribs Specification of Letters Patent.

, vert the common periodic oscillator Patented May 25, 1920.

1919. Serial No. 308,061.

or wings attached to the needle system and moving broadside through the liquid as previously proposed and employed in such compasses. In all cases the aim is to produce a high damping resistance as the filament or filaments move through the fluid inside the bowl, while at the same time the smallest possible addition is made to the moment of 1nert1a of the revolving mass of the needle system.

An aperiodic magnetic compass suitable for an'aeroplane is illustrated by way of example in the accompanying drawing, in which Figure 1 is a sectional side elevation of the compass, and I Fig. 2 is a perspective view drawn to a larger scale of the needle system detached.

a indicates the bowl of-the compass and b the stand or support therefor. c indicates a skeleton hemispherical dome which is constructed of ribs carrying at the summit the pivot d and girdled at the lower end by the ring e. To the ring e are attached two carriers f each of which holds three bar magnets g.

h, h are the damping filaments, here eight in number, which are attached to the dome c and project in the direction, of the cardinal v and quadrantal points. Letters N. E. S. W., abbreviations of the names of the cardinal points, are attached to the filaments which point in those directions respectively.

laims-- 1. A liquid magnetic compass armed with one or more filaments included in the needle system and adjusted so as to produce by their motion through the li uid a damping effect adequate to convert t e common periodic oscillatory movement of the magnetic compass into a movement of the kind usually termed dead-beat and herein referred to as aperiodic.

2. In a liquid magnetic compass, the combination with a needle. system, of relatively long filaments included in the needle system and extending radially from the compass axis to produce by their motion through the liquid a damping effect adequate to conmove ment of the compass into an aperiodic movement.

3. In a liquid magnetic compass, the comdamping effect adequate to convert the common periodic oscillatory movement of the compass into an aperiodic movement.

EDWARD FITZHARDINGE CAMPBELL, Administrator of George Richard Colin Campbell, dc-

ceasad.

GEOFFREY THOMAS BENNETT. 

